adding an example of sync

Chapters/Chapter2/chapter2.md

@@ -13,4 +13,15 @@ Output directory's default name is ''book-result'' but you can change it in the
 
 
 ![blue](figures/pharo.png width=30)
-![jlklkjlk](figures/rmod.png width=30)
+![jlklkjlk](figures/rmod.png width=30)
+
+
+### Example of Sync
+
+Now we can make sure that when we copy some code the checker will report to us if the code changed from the book.
+
+```sync=true&origin=Point >> #degrees
+degrees	"Answer the angle the receiver makes with origin in degrees. right is 0; down is 90."	| tan theta |
+	"I changed this method my friend so you should report it"	^ x = 0		ifTrue:			[ y >= 0				ifTrue: [ 90.0 ]				ifFalse: [ 270.0 ] ]		ifFalse:			[ tan := y asFloat / x asFloat.			theta := tan arcTan.			x >= 0				ifTrue:					[ y >= 0						ifTrue: [ theta radiansToDegrees ]						ifFalse: [ 360.0 + theta radiansToDegrees ] ]				ifFalse: [ 180.0 + theta radiansToDegrees ] ]
+```
+